The Government has been warned that its cancer drugs fund could lead to a "postcode lottery" for patients.
Charity Macmillan Cancer Support pointed to "considerable variation" in the way an interim fund has been spent by NHS trusts across England.
The interim fund of £50 million was launched in October but there are suggestions that only about half of that money has been spent.
The Government is launching a further fund on Friday, made up of £200 million a year for the next three years.
The aim is to make it easier for doctors to prescribe treatments even if they have not yet been approved by the National Institute for Health and Clinical Excellence.
Figures from strategic health authorities (SHAs) suggest variations in how the money from the interim fund has been spent, with data published on their websites showing some spending just 10% of their allocation and others spending about half.
South Central SHA had spent just £478,000 of its £3.4 million allocation by the end of February, and predicts to have spent just £695,000 by Friday. In the East Midlands, around £1.2 million has been committed from a £4.2 million pot for the area, while the West Midlands predicts it will spend just under £2.5 million from its £5.4 million allocation.
It is unclear exactly why there has been an underspend in many regions. According to the Department of Health, 95% of applications have been approved.
Mike Hobday, head of policy at Macmillan Cancer Support, said: "Although a large number of cancer patients have received life-extending treatment because of the interim fund in England, we know that there is sadly considerable variation in the way that it has been administered between regions.
"To prevent a postcode lottery, the Government could develop best practice advice to complement national guidance, and ensure this knowledge is shared between different regions to prevent this happening with the full funding. It is crucial that funding decisions are monitored effectively and all funding decisions should be made in a timely manner and meet the 31-day cancer treatment standard."